Development of ornamental Cannabis sativa L. cultivars: phytochemical, morphological, genetic characterization and propagation aspects

Due to its attractive variegated foliage, ornamental Cannabis cultivars offer new marketing opportunities. During the last years various chimera have been detected and, while most of them are still in process of selection, Phytoplant Research (PR) has recently obtained from the Community Plant Variety Office (CPVO) the provisional protection of plant breeder’s rights for the dioecious female cultivar ‘Divina’ (CPVO file number: 2017/0149; granted with decision N° EU 50045 of 16 July 2018) characterized by a stable variegated foliage of vegetatively propagated plants. ‘Divina’ has a distinctive “mottled yellow and green leaf” phenotype from the cultivar ‘Pilar’ where the mutated type chimera was detected and isolated from a mutated donor greenhouse growing plant. Both cultivars show the same genotype when nuclear DNA fingerprinting is performed by using 15 SSR molecular markers. Additionally, by using a molecular marker for Δ9-THCA/CBDA synthases it was confirmed that only the alleles for CBDA synthase can be detected in both cultivars; gas chromatography analysis also confirmed that both cultivars had a CBD chemotype. The content of the psychotropic compound Δ9-THC in inflorescences of ‘Divina’ plants was lower than 0.4% in all the samples analysed at our laboratories. Microscope observations of “yellow” portions of stalks, leaves and inflorescence bracts confirm the presence of bulbous, sessile- and capitate-stalked trichomes. ‘Divina’ cuttings are more prone to fungal disease during in vivo rooting stage than ‘Pilar’ cuttings, however, satisfactory percentages of true to type rooted cuttings can be achieved by adopting good propagation practices. A protocol for all the stages of in vitro micropropagation has been established at our laboratories. When considering the sexual propagation of the cultivar, all the F₁-hybrid offspring obtained by crossing a dioecious “green leaf” male plant with a ‘Divina’ plant showed a “green leaf” phenotype.